Premium
Heterocyclization Reactions of Conjugated Heterocumulenes. Synthesis of Pyridine Derivatives by a Tandem Aza Wittig/Electrocyclization Strategy
Author(s) -
Molina Pedro,
Arques Antonio,
Fresneda Pilar M.,
Vinader Maria Victoria,
De La Concepciòn FocesFoces Maria,
Cano Félix Hernandez
Publication year - 1989
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19891220217
Subject(s) - chemistry , nitromethane , conjugated system , wittig reaction , electrocyclic reaction , pyridine , acetone , molar ratio , medicinal chemistry , ylide , tandem , ring (chemistry) , organic chemistry , catalysis , materials science , composite material , polymer
The aza Wittig reaction of iminophosphorane 3 with isocyanates leads to conjugated carbodiimides 4 , which undergo electrocyclic ring closure to give ethyl 2‐pyridinecarboxylates 5 . Iminophosphorane 9 reacts with nitromethane and acetone in a 1:1 molar ratio to form 10 and 11 , respectively. Reaction of 9 with nitromethane in 1:3 molar ratio yields the iminophosphorane 12 . The structure of 12 has been established by X‐ray crystallography. Iminophosphoranes 10 and 11 react with isocyanates or carbon dioxide to give the pyrazolo[3,4‐ b ]pyridines 13 , 15 and 14 , 16 , respectively.